This invention relates to electronic musical instruments and more particularly to electronic musical instruments by a time division multiplex tone selection mode.
In a prior art electronic musical instrument, tone generators are provided for respective keys (notes) for generating signals (tone signals) having frequencies defining the tone pitches of respective keys, whereby when a certain key is depressed, a tone signal corresponding to that key is produced. When there is any other key which is depressed concurrently with said key, a tone signal corresponding to the other key is also generated simultaneously. The tone signals thus produced are mixed together and then sent to a tone color circuit to be imparted with a definite tone color. As a result, tone signals are produced to sound musical tones corresponding to the depressed keys.
Although such a prior art electronic musical instrument can simultaneously generate a plurality of musical tones, it is necessary to provide a plurality of tone generators for generating tone signals of the same number as the keys. Accordingly, there is a defect that the number of the tone generators increases in proportion to the increase in the number of keys. Since the tone generator utilizes an analogue oscillator, it is difficult to construct the tone generator by integrated circuits, and since a number of frequency dividers are required, the size of the musical instrument would become large and the cost high.
Furthermore, in an electronic musical instrument, there is added a coupler effect device which simultaneously switches a plurality of tone signals having a predetermined relationship (for example an octave relationship) corresponding to a depressed key for providing a coupler effect. However, such a coupler effect device requires to provide a plurality of key switches or switching circuits for each key thus complicating the construction. Moreover, there is a problem that it is impossible to increase the number of the tone signals that can be simultaneously keyed by the coupler effect device.
Although an electronic musical instrument utilizing digital technique has recently been developed, in the electronic musical instrument of this type the number of musical tones that can be produced simultaneously is limited. For this reason, as the number of the simultaneously generated tones is increased, the circuit construction becomes complicated. Furthermore, in the electronic musical instrument of this type, in order to provide aforementioned coupler effect it is necessary to further increase the number of the simultaneously generated tones thus increasing the size of the electronic musical instrument.